Over the last year, the concept of ‘private blockchains’ has become very popular in the broader blockchain technology discussion. Essentially, instead of having a fully public and uncontrolled network and state machine secured by cryptoeconomics (eg proof-of-work, proof-of-stake), it is also possible to create a system where access permissions are more tightly controlled, with rights to modify or even read the blockchain state restricted to a few users, while still maintaining many kinds of partial guarantees of authenticity and decentralization that blockchains provide. Such systems have been a primary focus of interest from financial institutions and have, in part, led to a backlash from those who see such developments as either compromising the whole point of decentralization or being a desperate act of dinosaurish middlemen trying to stay relevant (or simply committing the crime of using a blockchain other than bitcoin). However, for those who are in this fight simply because they want to figure out how to best serve humanity, or even pursue the more modest goal of serving their customers, what are the practical differences between the two styles? First, what exactly are the options at hand? To summarize, there are generally three categories of blockchain-like database applications: …